Monday, April 24, 2017


Here's a brief video detailing the basic techniques used on our LOLz.  See the picture for the revised version of the qualitative conservation of energy equations.

Set the energy stored at A equal to the energy stored at B, use subscripts for type and position.

Monday, April 3, 2017

Follow Up From Circular Motion Lab

Here are some sample graphs of Fuc vs Vtan and Fuc vs. Angular Velocity

And here's the analysis for the Fuc v. Angular Velocity graph.  The trend follows y=ax^2, "y" is the Fuc in Newtons, and x is the angular velocity in rad/s.  When you're doing dimensional analysis, 'rad' doesn't really count as a unit, so the unit for angular velocity is basically 1/s.  That angular velocity is squared in the equation means that the unit for x^2 is 1/s^2.  The units on the left-side of the equation are Newtons, or kg*m/s^2 which means that the units on the constant "a" in the equation have to combine with the units on x^2 to give the same units.  So what the heck is kg*m, well, it suggests that you have things that you held constant in the data collection that had units of kg and meters.  Your stopper mass didn't change, so that's the kg, and your radius didn't change, that's the meters.  When this group multiplies those two things together, they get something darn close to 0.0083.  So the general form of their equation would be 
Fuc=radius*mass (of thing going in a circle)*angular velocity^2

For the Vtan version of the lab, x^2 in the equation has the units (m/s)^2 because you're squaring the Vtan, so what are the units on that constant? What would you multiply times the m^2/s^2 (that we get from x^2) in order to get kg*m/s^2, it needs to bring kg into the equation, and get rid of the "squared" on the meters.  So kg/m it is then.  That makes the general form of that equation

So now, get some practice with those two equations by attacking the worksheet you picked up on the way in today!

Wednesday, March 8, 2017

Sick and tired of being sick and tired....

...sorry gang, I know this is less than ideal.  Fever was worse on Wednesday, so I didn't get in to verify where you left off the day before.  Hopefully I'll be back on Friday so we can tie up the loose ends before break.  I'd like to quiz on Friday, but let's just worry about quizzing once we're back from spring break (and not until a couple of days into the week.)  Anyway, the videos from the other day dealt with objects that both initially start from rest.  Here's some follow up to go along with that and give you some practice at analyzing explosions.  Don't get too excited, this is a public school, our budget doesn't allow for videos of real explosions, you just get these videos of kids pooshing off of each other.  Craft IF Chartz for each of these situations, use the info on the video to determine things like velocity, and pmomentum.  Fit all that onto a whiteboard (are there any blank ones left? group some shorties together if you must!) and share it out near the end of the hour (it's ok if all groups aren't all the way done, least done group explains there answers for the first part, and you can just follow along from there.)  You don't need to put these in Logger Pro, you can just get the info that you need directly from the videos (hopefully.)

Anyway, grab a laptop (or use your own if it's fancy) and some whiteboards and have at these videos.

Video 1  Construct fully quantitative IF Chartz

Video 2  Construct fully quantitative IF Chartz

Video 3  Determine the mass of the gentleman on the right.

Class Instructions for Wednesday, March 8th

If you have completed presenting whiteboards for the problems 3-9 on the IF Chartz packet, go ahead and move on to the problems on this new worksheet, Momentum Problems 2.  You'll need to use the Impulse (product of UnBalanced Force and Time Interval) and Change in Pmomentum (product of mass and change in velocity) equation to solve some of these problems.  Recognize that "Impulse" would be found on a graph of Fu vs. t by finding the area between the graph and the x-axis.